List the top words used in a file and the number of times they are used.

TopWords.cs

using System;
using System.IO;
using System.Linq;
using System.Text.RegularExpressions;

namespace TopWords {
    internal class Program {
        private static void Main(string[] args) {
            const int maxWords = 298;
            const int minWordLength = 4;

            var file = args[0];
            var text = File.ReadAllText(file).ToLower();
            var regex = new Regex("[^a-zA-Z0-9' ]");

            text = text.Replace(Environment.NewLine, " ");
            text = regex.Replace(text, " ");

            var words =
                text.Split(' ')
                    .Where(word => word.Length >= minWordLength)
                    .GroupBy(word => word)
                    .Select(group => new {Word = group.Key, Count = group.Count()})
                    .OrderByDescending(word => word.Count)
                    .Take(maxWords)
                    .ToList();

            var lines = words.Select(word => {
                var count = word.Count.ToString("d4");
                var position = (words.IndexOf(word) + 1).ToString("d3");
                return string.Format(" {0} {1} {2}", position, count, word.Word);
            });

            Console.WriteLine();

            foreach (var line in lines) {
                Console.WriteLine(line);
            }

            Console.ReadLine();
        }
    }
}